1. Field of the Invention
The invention is related to a charge control agent, and the toner containing such charge control agent.
2. Description of the Related Art
Charge control agents mainly comprised of metal complex has been extensively used in various areas, i.e. in the toner used in forming developer for developing an imaging in electrophotographic technology, as a componential material in the making of such toner (see, e.g., Japanese Patent Publication 63-61347, Japanese Patent Publication 2-16916, Japanese Patent Publication 2002-53539, Japanese Patent 2531957, Japanese Patent Publication 7-97530, and Japanese Patent Publication 2005-121776).
The metal complex normally used as charge control agent in toners, including generally known azo-metal complex and salicylate-metal complex.
On one hand, in an imaging forming apparatus using electrophotographic technology to form an imaging, it is necessary to heat the toner imaging recorded on a transfer material in order to fix the imaging. In recent years, for the purpose of energy saving, low temperature fixing is preferred.
However, in the chemical structure of azo-metal complex and salicylate-metal complex, the metal ion often tends to detach from the structure. The result is that in the toners using azo-metal complex or salicylate-metal complex as charge control agent, the detached metal ion may bridge with the resin structure which is another ingredient of the toner. This will cause an increase of the softening point of the toner. Thus high quality imaging in low temperature fixing can not be obtained. In addition, when the environment humidity varies, the imaging quality also varies obviously. These are existing problems.
Thus, there were some suggestions to use metal-free chemicals such as calixarene compounds as a charge control agent for toner. Comparing toners using such charge control agent and toners using metal-complex as charge control agent, the charge characteristics of former are not uniform, and the charge amount of toner particles are not evenly dispersed. The toner particles which are not sufficiently charged will cause the dusting and fogging of toner imaging.